Chlorination process



United States CHLORINATION PROCESS Edwin K. Plant, Pittsburgh, Pa.,assignor to Columbia- Southern Chemical Corporation, Allegheny County,Pa., a corporation of Delaware No Drawing. Application April 29, 1954,Serial No. 426,603

11 Claims. (Cl. 23-87) This invention relates to the chlorination ofores. It is well established that many metal bearing materials,particularly metal oxide bearing materials, may be chlorinated atelevated temperatures. A wide variety of literature has been developedin this field and the processes have been commercially used. Forexample, titanium bearing materials, such as ilmenite, rutile,essentially pure titanium dioxide, titanomagnetite, and like ores orother materials containing 10 to 50 percent or more of titanium, havebeen chlorinated successfully. Typical processes for effecting suchchlorination are described in U. S. Patents Nos. 2,184,884, 2,184,885,2,184,887, 2,253,470, and 2,253,471.

Typical chromium ores or chromium bearing materials which preferablycontain in excess of about 10 percent chromium may be chlorinated. Suchprocesses are described in U. S. Patents Nos. 2,185,218, 2,240,345, and2,368,323. These processes and other processes for chlorination ofchromium oxide bearing ores, as well as metallic ferrochromium and thelike, are well known in the art.

Tin ores which contain in excess of to percent of tin also have beensubjected to chlorination as described in U. S. Patent No. 2,345,210. Inall of the above mentioned patents, the chlorination of ores containingother metallic components, including iron, aluminum, and the like, arealso disclosed.

Various other metallic bearing materials, notably oxide bearingmaterials which contain aluminum, zirconium, arsenic, beryllium,bismuth, germanium, gold, tellurium, columbium, and the like, may besubjected to chlorination for production of the corresponding metalchlorides. In many cases it is desired to avoid formation of mixtures ofchlorides and consequently it is not uncommon to chlorinate relativelypure metal compounds such as titanium carbide, titanium oxide, or thecorresponding oxides, carbides, nitrides, and the like, of other metals.

In the practice of the above described chlorination processes,briquettes of the metal ore or metal oxide or like metal bearingmaterial with carbon are prepared. The amount of carbon normally used isthat stoichiomctrically required to reduce a major portion (usually atleast one-half) or even all of a metal oxide or like compound to themetallic state.

In these processes, the briquettes are placed in a shaft furnace and aresubjected to contact with gaseous chlorine at an elevated temperature,normally ranging above about 500 C., and usually ranging from about 800to 1200 C., and the chlorination occurs with the chlorides beingvaporized and condensed in suitable condensation equipment.

Considerable ditficulty is observed due to the fact that the briquettestend to disintegrate during chlorination. As a consequence, substantialquantities of unchlorinated material tend to be swept away from thereaction furnace by the chlorinating gases and the evolved atent2,805,120 Patented Sept. 3, 1957 ice vapors of chlorination. Thismaterially reduces the efficiency of the process and increases its cost.Furthermore, it complicates the problem of condensing the vapors andrecovering them in a pure or substantially pure form.

According to the present invention, a novel method has been providedwhereby briquettes which tend to disintegrate less readily are produced.In accordance with this method, the metal oxide bearing material, suchas titanium dioxide, ilmenite ore, chromite ore, or the like, is mixedwith a bituminous coal, preferably a soft coking coal, and the mixedproduct is heated while tumbling at a temperature at which components ofthe coal (tar, high boiling hydrocarbons, and the like) are fused atleast to a degree that they are sticky or adhesive. As a consequence oftumbling of this character, the product forms into balls or likeagglomerates. These agglomerates are then calcined at an elevatedtemperature, preferably high enough to effect removal of substantiallyall of the volatile hydrocarbons from the product. The resulting productis found to be well bonded and shows little or no tendency todisintegrate during chlorination.

According to a further embodiment of the invention, it is foundadvantageous to prepare these briquettes by incorporating, in additionto the coal and ore or like titanium or other metal bearing material, asubstantial quantity of a previously carbonized bituminous coal,preferably a carbonized mixture of the metal oxide bearing material andbituminous coal. Such previously carbonized material should have aparticle size substantially less than that desired in the briquettes,and usually about one-eighth inch in diameter or below. Such materialmay be obtained by breaking up or grinding previously formed carbonizedbriquettes. By incorporating such a previously carbonized material inthe coal-metal oxide bearing material to be briquetted, it is found thatthe previously carbonized material tends to serve as nuclei upon whichthe balls may build up to the size desired.

The practice of the above described invention will be discussed indetail as applied to the chlorination of titanium oxide bearingmaterials such as ilmenite, titanium oxide or rutile. It will beunderstood, of course, that the embodiments discussed with reference totitanium bearing materials may also be applied to the preparation ofbriquettes for chlorination of other metal bearing materials such asthose mentioned above.

Titanium bearing materials to be chlorinated normally contain thetitanium in the form of oxide and may contain more or less iron whichalso is present as an oxide. The titanium content of the materialnormally is in exccss of about it) percent titanium. Rutile may containvery little iron, for example, 1 to 2 percent iron. Also, the materialto be treated may have been processed previously in order to remove aportion of the iron. On the other hand, ilmenite ore contains asubstantial amount of iron, usually ranging well above 10 percent iron.A typical ilmenite ore is one which contains about 26 percent iron and35 percent titanium, both metals being present in the oxide form.Various other ores containing 10 to 35 percent iron and 20 to percent ormore of titanium may be subjected to treatment.

In the practice of the invention, the titanium dioxide or titanium oreis mixed with bituminous coal. The bituminous coal preferably should beone which is a soft coking coal. Coals having a low ash content normallyare preferred in order to avoid contamination of the product. Pittsburghseam bituminous coal and like coals capable of producing coal briquettesare quite suitable.

The amount of coal should be sufficient to supply the stoichiometricamount of carbon required to reduce the titanium present as oxide tometallic state. Where iron or other metal is present, proper allowancemust be made to provide the amount required to reduce these metals. Thisis particularly true of a metal such as iron which tends to chlorinatebefore titanium. The amount of coal used for this purpose will depend toa considerable degree on the amount of fixed carbon in the coal. Ingeneral, however, the amount is in the sufiicient proportion toestablish about to 100 percent by weight of carbon in the ultimatebriquette, based upon the weight of the titanium oxide undergoingchlorination. Larger amounts of carbon may be used but are usuallyunnecessary. In addition, a quantity of a previously carbonized mixtureof titanium oxide bearing material and coal is added. The particle sizeof this material preponderantly is about one-fourth inch in diameter orbelow. The mixed materials are then fed into a rotating drum which isheated to a temperature at which the coal becomes sticky due to fusionof organic components therein. The exact temperature required dependsupon the nature of the coal. Temperatures ranging from about 250 to 600C. are normally adequate. A good average temperature is about 400 to 450C. As a consequence of the tumbling, the mixture of the coal and the oretends to collect upon the nuclei of the previously carbonized materialand to form agglomerate which, as they are tumbled, tend to shapethemselves into balls or rounded briquettes. This process is continueduntil the balls have built up to a desirable size. This size is largelya matter of choice but normally ranges from /2 to 2 inches in diameter.

Following formation, the balls or briquettes are placed in a calciningfurnace and are calcined in order to remove hydrocarbon components. Thiscalcination may be conducted suitably in a rotary furnace. Thetemperature of calcination is subject to some variation depending uponthe time of calcination and also upon the nature of the volatilecomponents, but normally ranges from 750 to 1200" C.

Of course, the calcination is effected under conditions such as to avoidburning of the briquettes. That is, air is excluded and the atmospherein which the product is calcined is effectively a reducing atmosphere.

Following the production of the briquettes, they are subjected tochlorination with or without cooling. The chlorination may be effectedmost readily by introducing the briquettes into a shaft furnace wherebyto form a bed of briquettes, introducing chlorine into the bottom of thebed, and allowing the chlorine to permeate the bed and etfect thechlorination. The reaction proceeds at a temperature well about 500 C.,usually in the range Example I The ore used is ilmenite ore having thefollowing analysis:

Percent by weight Titanium 31.3 Iron 23.3 SiOz 4.3 A1203 2.5

Magnesium and calcium 0.9

Two thousand pounds of this ilmenite ore is mixed with 1430 pounds of alow ash, soft-coking, Pittsburgh seam bituminous coal, and 860 pounds ofa previously carbonized mixture of coal and ilmenite ore. The ore usedwas ground to a degree where 98 percent passed through 200 mesh. Thecoal had a particle size of less than onefourth inch. The previouslycarbonized material had a particle size of less than one-eighth inch.

The resulting mixture was fed into a rotating drum 8 feet in diameterand 16 feet long and was heated to a temperature of 500 C. The drum wasrotated at approximately 5 R. P. M. and the mixture was tumbled in thisdrum for a period of about 35 minutes. Thereafter, the heat was turnedoff and the tumbling continued for about 10 minutes to harden theresulting balls which were produced, and the resulting product wasdischarged from the drum and was lightly crushed and screened to give aproduct having the size of approximately id. x 4 inches. The fines whichwere screened from this product were recycled as a carbonized mixture ofcoal and ore for production of a further batch of briquettes.

The resulting briquettes were chlorinated in a shaft furnace having aninternal diameter of 16 inches by feeding the briquettes to a reactionbed in the furnace in which chlorination was effected at approximately900 to 1000 C. Over a period of 58 hours, 6,164 pounds of the briquetteswere fed at the rate of 62% pounds each /2 hour to the bed until theentire amount of 6,164 pounds had been fed. During the period of 58hours, 12,656 pounds of chlorine was fed into the reactor at asubstantially uniform rate. Approximately 4,621 pounds of crude titaniumtetrachloride was produced. During the operation, essentially noblowover of material, due to disintegration of the briquettes, tookplace.

It will be understood that the process disclosed in the above identifiedexample may be applied to other materials, including pure titaniumdioxide, titanomagnetite, and various titanium dioxide concentrates.Moreover, it is possible to effect a selective chlorination of the ironfrom titanium in ilmenite by limiting the amount of carbon, as isdescribed in U. S. Patent No. 2,184,884. Thus, the briquettes in such acase may be prepared using a substantially lower concentration ofcarbon.

The process also may be used in the chlorination of the other metalbearing materials, following the practice disclosed in the aboveidentified example, with or without the modifications taught in any ofthe above identified patents.

Although the present invention has been described with reference to thespecific details of certain embodiments, it is not intended that suchdetails shall be regarded as limitations upon the scope of the inventionexcept insofar as included in the accompanying claims.

What is claimed:

1. A method of preparing a metallic chloride which comprises mixing amaterial which comprises a finely divided oxide of a metal which forms avolatile chloride with an amount of pulverulent bituminous coal having aparticle size below about A inch at least equal to the amountstoichiometrically required for reduction of said metal oxide tometallic state, tumbling said mixture at a temperature of 250 to 600 C.whereby the coal becomes adhesive and agglomerates of coal and saidfinely divided material are built up, thereafter calcining the resultingagglomerates to remove hydrocarbon components, and chlorinating theagglomerates thus obtained.

2. The process of claim 1 wherein the agglomerates are calcined at atemperature of 750 to 1200 C. to remove hydrocarbons prior tochlorination.

3. The process of claim 1 wherein there is incorporated in the mixtureor ore and coal, particles of a previously carbonized mixture of cokeand said ore.

4. A method of preparing titanium tetrachloride which comprises mixing afinely divided ore which contains at least 10 percent titanium in theform of oxide with an amount of pulverulent bituminous coal having aparticle size below about inch suflicient to provide in the mixture atleast if) percent by weight of carbon, heating the mixture to atemperature of 250 to 600 C. whereby the coal becomes adhesive, tumblingthe mixture at said temperature and thereby forming agglomeratescomprising particles of ore and particles of coal bonded together,thereafter calcining the resulting agglomerates to remove hydrocarbon,and chlorinating the resulting agglomerates to form and vaporizetitanium tetrachloride.

5. A method of preparing a metal chloride which comprises mixing afinely divided ore which contains a metal oxide capable of forming ametal chloride which is volatile at a temperature below 600 C. with anamount of bituminous coal at least sutficient to provide in the mixtureat least 10 percent by weight of carbon, heating the mixture to atemperature at which the coal becomes adhesive, tumbling the mixture atsaid temperature and thereby forming agglomerates comprising particlesof ore and particles of coal bonded together, thereafter calcining theresulting agglomerates to remove hydrocarbon, and chlorinating theresulting agglomerates at a temperature above 500 C.

6. The process of claim wherein the temperature of heating duringtumbling is 250 to 600 C.

7. A method of preparing a metal chloride which comprises mixing afinely divided ore which contains a metal oxide capable of forming a.metal chloride which is volatile at 600 C. with an amount of bituminouscoal sulficient to provide in the mixture at least percent by weight ofcarbon, heating the mixture to a temperature of 250 to 600 C. wherebythe coal becomes adhesive, tumbling the mixture at said temperature andthereby forming agglomerates comprising particles of ore and particlesof coal bonded together, separating the agglomerates into a coarsefraction and a fine fraction, mixing the fine fraction with a furtherportion of said finely divided ore and an amount of bituminous coalsuflicient to provide in the mixture at least 10 percent by weight ofcarbon thereby forming a second mixture, heating the second mixture to atemperature of 250 to 600 C. whereby the coal becomes adhesive, tumblingthe second mixture at said temperature whereby the particles of saidfine fraction serve as nuclei and agglomerates comprising particles ofore and coal bond thereto thus forming further agglomerates, andchlorinating further agglomerates thus formed.

8. A method of preparing titanium tetrachloride which comprises mixing afinely divided ore which contains at least 10 percent titanium in theform of oxide with an amount of pulverulent bituminous coal having aparticle size below about A inch sufiicient to provide in the mix tureat least 10 percent by weight of carbon, heating the mixture to atemperature of 250 to 600 C. whereby the coal becomes adhesive, tumblingthe mixture at said temperature and thereby forming agglomeratescomprising particles of ore and particles of coal bonded together,separating the agglomerates into a coarse fraction and a fine fractionmixing the fine fraction with a further portion of said finely dividedore and an amount of bituminous coal suflicient to provide in themixture at least 10 percent by weight of carbon thereby forming a secondmixture, heating the second mixture to a temperature of 250 to 600 C.whereby the coal becomes adhesive, tumbling the second mixture at saidtemperature whereby the particles of said fine fraction serve as nucleiand agglomerates comprising particles of ore and coal bond thereto thusforming further agglomerates, and chlorinating further agglomerates thusformed and thereby producing titanium tetrachloride.

9. The process of claim 7 wherein the coarse fraction is chlorinated ata temperature of at least 500 C. after separation from the finefraction.

10. The process of claim 1 wherein the mixture is tumbled at atemperature of 400 to 450 C.

11. The process of claim 5 wherein the resulting agglomerates arecalcined at 750 to 1200' C. to remove volatile hydrocarbons.

References Cited in the file of this patent UNITED STATES PATENTS1,179,394 Barton Apr. 18, 1916 2,184,887 Muskat et a]. Dec. 26, 19392,253,471 Muskat et al. Aug. 19, 1941 2,453,050 Turbett Nov. 2, 19482,658,039 McFarlin Nov. 3, 1953 2,675,307 Klugh et al Apr. 13, 19542,723,903 Cyr et al. Nov. 15, 1955 OTHER REFERENCES Perry's: ChemicalEngineers Handbook, pages 930-932, third ed., 1950. McGraw-Hill BookCo., Inc., N. Y.

Handbook of Chemistry and Physics, Hodgrnan- Lange, fourteenth ed., page857. Chemical Rubber Publishing Co., Cleveland, Ohio.

1. A METHOD OF PREPARING A METALLIC CHLORIDE WHICH COMPRISES MIXING AMATERIAL WHICH COMPRISES A FINELY DIVIDED OXIDE OF A METAL WHICH FORMS AVOLATILE CHLORIDE WITH AN AMOUNT OF PULIVERULENT BITUMINOUS COAL HAVINGA PARTICLE SIZE BELOW ABOUT 1/4 INCH AT LEAST EQUAL TO THE AMOUNTSTOICHIOMETRICALLY REQUIRED FOR REDUCTION OF SAID METAL OXIDE TOMETALLIC STATE, TUMBLING SAID MIXTURE AT A TEMPERATURE OF 250 TO 600*C.,WHEREBY THE COAL BECOMES ADHESIVE AND AGGLOMERATATES OF COAL AND SAIDFINELY DIVIDED MATERIAL ARE BUILT UP, THEREAFTER CALCINING THE RESULTINGAGGLOMERTRATES TO REMOVE HYDROCARBON COMPONENTS, AND CHLORINATING THEAGGLOMERATES THUS OBTAINED.